Battery monitor apparatus

ABSTRACT

A battery monitor apparatus includes unit batteries connected in series; a battery pack including battery modules connected in series by conductive members, each battery module including two or more of the unit batteries; voltage detection ICs to detect voltages of the unit batteries and the conductive members in circuit intervals connected in series, by potential differences of the circuit intervals; and an electronic control unit to monitor states of the unit batteries. At least one voltage detection IC detects a voltage of at least one of the two unit batteries adjacent to a conductive member, and detects a voltage of the conductive member adjacent to the two unit batteries. The electronic control unit monitors the states, based on the voltages of the unit batteries, and one or more of the voltages of the conductive members detected by one of the voltage detection ICs.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of priority of JapanesePriority Application No. 2015-023555, filed on Feb. 9, 2015, the entirecontents of which are hereby incorporated by reference.

FIELD

The disclosures herein generally relate to a battery monitor apparatusto monitor states (voltages and the like) of respective unit batteriesin a battery pack that has multiple battery modules connected byconductive members such as bus bars, and each battery module includessome of the unit batteries connected in series.

BACKGROUND

Conventionally, a power storage apparatus has been known that includesan integrated circuit (a battery monitor IC) to detect voltages of unitbatteries connected in series in a battery pack, and to monitor statesof the respective unit batteries based on the voltages of the unitbatteries detected by the battery monitor IC (see, for example, JapaneseLaid-open Patent Publication No. 2013-162635).

FIGS. 1A-1B are diagrams that illustrate an example of a battery monitorapparatus that detects voltages of unit batteries included in a batterypack by using voltage detection ICs as in the conventional art (e.g.,Japanese Laid-open Patent Publication No. 2013-162635). Specifically,the diagrams illustrate an example of a configuration to detect voltagesof multiple unit batteries (battery cells C1 to C54) that are connectedin series and included in a battery pack 100 constituted with multiplebattery modules 100-1 and 100-2, by voltage detection ICs 200 (200-1 to200-8).

Referring to FIG. 1A, each of the voltage detection ICs 200 detectsvoltages of eight battery cells that are connected in series, by voltagedetection lines that are connected to nine ports (channels ch1 to ch8).That is to say, in each of the voltage detection IC 200, a voltagedetection point (a voltage detection line), which corresponds toelectrodes of two adjacent unit batteries connected with each other, isshared by two adjacent channels. This decreases the number of ports andthe number of wires of a voltage detection IC, compared to a case wherevoltages are detected by connecting the respective electrodes of a unitbattery with a voltage detection IC one by one. Therefore, the cost andthe circuit size can be reduced.

On the other hand, when adopting such a configuration, if a battery packis constituted with multiple battery modules connected by conductivemembers, voltages of some unit batteries (e.g., the voltage of thebattery cell C28 in FIG. 1A) may be detected as voltages that includevoltage drops caused by resistance of the conductive members.Specifically, if the number of unit batteries included in a batterymodule is not a multiple of the number of channels of the voltagedetection IC, some voltage detection ICs may detect voltages of unitbatteries over multiple battery modules. Therefore, at least one ofdetected voltages of unit batteries adjacent to a conductive memberconnecting two battery modules with each other, may include a voltagedrop due to the resistance of the conductive member. Usually, since unitbatteries in a battery module are placed closely together, theirelectrodes may be directly connected, or connected by connection membershaving very short length. Therefore, the resistance of such an“intra-module” connection member has little influence on the voltages ofunit batteries, which are to be detected by the voltage detection IC. Incontrast to this, a conductive member connecting battery modules witheach other has a certain length due to a layout restriction and/ormaintainability. Therefore, the resistance of such an “inter-module”conductive member has very large influence on the voltages of unitbatteries, which are to be detected by the voltage detection IC. In thiscase, a voltage including a voltage drop due to the resistance of theconductive member connecting battery modules with each other is detectedas the voltage of a unit battery, and hence, precision of the detectedvoltage of the unit battery may be reduced, and it may not be possibleto monitor the state of the unit battery appropriately.

Therefore, as an example, as illustrated in FIG. 1B, the apparatus maybe configured so that no voltage detection IC is provided that detectsvoltages of unit batteries over multiple battery modules. In this case,the influence of the resistance of an “inter-module” conductive membercan be excluded, and a voltage detection IC can detect the voltage of aunit battery on the boundary of modules, with high precision.

However, if the apparatus is configured so that no voltage detection ICis provided that detects voltages of unit batteries over multiplebattery modules, the number of voltage detection ICs needs to beincreased as many as the number of “inter-module” conductive members.Especially, considering maintainability and the like, if a batterymodule is adopted that is constituted with a comparatively less numberof unit batteries, the number of battery modules included in a batterypack may increase comparatively greater. In this case, the number ofvoltage detection ICs to be installed increases proportional to thenumber of battery modules. Therefore, the cost and circuit size mayincrease due to the increased number of voltage detection ICs to beinstalled.

In view of the above problem, it is an object of at least one embodimentto provide a battery monitor apparatus that can detect voltages of unitbatteries in a battery pack having multiple battery modules connected inseries where each battery module includes multiple unit batteriesconnected in series, and can monitor the unit batteries appropriately bythe states of the respective unit batteries based on the detectedvoltages, without increasing the cost and circuit size of the apparatus.

SUMMARY

According to an embodiment, a battery monitor apparatus includes aplurality of unit batteries connected in series; a battery packincluding a plurality of battery modules connected in series byconductive members, each of the battery modules being configured toinclude two or more of the unit batteries connected in series among theplurality of the unit batteries; a plurality of voltage detection ICsconfigured to detect voltages of circuit elements including theplurality of unit batteries and the conductive members in a plurality ofcircuit intervals connected in series, by potential differences betweenendpoints of the circuit intervals, and to detect voltages of two ormore of the unit batteries connected in series among the plurality ofthe unit batteries; and an electronic control unit configured to monitorstates of the unit batteries. At least one of the voltage detection ICsdetects a voltage of at least one of the two unit batteries adjacent toone of the conductive members, and detects a voltage of the conductivemember adjacent to the two unit batteries. The electronic control unitmonitors the states, based on the voltages of the unit batteriesdetected by the voltage detection ICs, and the voltage of the conductivemember detected by said at least one of the voltage detection ICs.

According to an embodiment, it is possible to provide a battery monitorapparatus that can detect voltages of unit batteries in a battery packhaving multiple battery modules connected in series where each batterymodule includes multiple unit batteries connected in series, and canmonitor the unit batteries appropriately by the states of the respectiveunit batteries based on the detected voltages, without increasing thecost and circuit size of the apparatus.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a diagram that illustrates an example of a configuration inwhich battery monitor ICs detect voltages of unit batteries included ina battery pack;

FIG. 1B is a diagram that illustrates an alternative example of aconfiguration in which battery monitor ICs detect voltages of unitbatteries included in a battery pack;

FIG. 2 is a block diagram that illustrates an example of a configurationof a vehicle including a battery monitor apparatus according to anembodiment;

FIG. 3 is a block diagram that illustrates an example of a configurationof a battery monitor apparatus according to an embodiment;

FIG. 4 is a diagram that compares the voltage of a battery cellpositioned at an end on the lower potential side of a battery module,with the voltage of the other one of the battery cells, when thevoltages are detected by a monitor IC; and

FIG. 5 is a flowchart that schematically illustrates an example of avoltage correction process by a battery monitor apparatus (or a batteryECU) according to an embodiment.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments will be described with reference to thedrawings.

FIG. 2 is a block diagram that illustrates an example of a configurationof a vehicle including a battery monitor apparatus 1 according to anembodiment. FIG. 3 is a block diagram that illustrates an example of aconfiguration of the battery monitor apparatus 1 according to theembodiment. Note that in FIG. 2, a solid line represents a power supplyline, a dotted line represents a communication line, and a double linerepresents a motive power transfer line.

The battery monitor apparatus 1 is built in a vehicle (e.g., aseries-parallel-type, hybrid vehicle), and monitors a state of a batteryunit 10 including battery cells C1-C54, which are unit batteries,configured to be capable of supplying power to a motor 50, which is oneof driving force sources of the vehicle.

Note that the battery unit 10 (battery cells C1-C54) is discharged whenit supplies power (of three-phase alternating current (AC)) to the motor50 via a motor inverter 70. Also, the battery unit 10 (battery cellsC1-C54) is charged when the power generated by a generator 60 having anengine 40 as a motive power source, which is another of the drivingforce sources of the vehicle, is supplied to the battery unit 10 asdirect current (DC) power via a generator inverter 80. Also, the batteryunit 10 (battery cells C1-C54) is charged when regenerative power (ofthree-phase AC) by the motor 50 functioning as a power generator whenthe vehicle decelerates, is supplied to the battery unit 10 as DC powervia the motor inverter 70.

The battery monitor apparatus 1 includes the battery unit 10 and abattery electronic control unit (ECU) 20. Also, the vehicle includes anHV-ECU 30 as an element relating to the battery monitor apparatus 1.

Note that in the following, the inside of the battery unit 10 outputtinga high voltage may be referred to as a “high-voltage” system, and theinside of the battery ECU 20 (except for an interface part with thebattery unit 10) driven by a low voltage may be referred to as a“low-voltage” system.

The battery unit 10 is configured to include a battery pack 11 andmonitor integrated circuits (ICs) 12.

The battery pack 11 is configured to have multiple unit batteries (54battery cells C1-C54 in the embodiment) connected in series.Specifically, the battery pack 11 is configured to have multiple batterymodules (18 battery modules MOD1-MOD18 in the embodiment) connected inseries by conductive members CBL1-CBL17 (for example, bus bars orconnection wires) where each battery module has two or more unitbatteries (three battery cells in the embodiment) connected in seriesamong the battery cells C1-C54. By configuring a battery pack with acomparatively large number of battery modules in this way, even if afailure occurs with some battery modules, a minimum number of units(battery modules) need to be replaced, and hence, the maintenance costcan be reduced.

The battery cells C1-C54 are 54 unit batteries. Each of the batterycells C1-C54 may be a unit cell of, for example, a lithium ion battery.

Note that the battery cells C1-C54 may be any other elements as long asthey are unit batteries that can be charged and discharged, for example,another type of secondary batteries (nickel-hydrogen batteries) orcapacitors. Also, the number of battery cells (54 cells) included in thebattery pack 11 and the number of battery modules (18 modules) are justexamples, and the numbers may be determined discretionally.

Each of the battery modules MOD1-MOD18 is configured to have threebattery cells among the battery cells C1-C54, that are seriallyconnected and contained in a prescribed housing or the like.Specifically, the battery modules MOD1, MOD2, and MOD18 contain thebattery cells C1-C3, the battery cells C4-C6, . . . , and the batterycells C52-C54, connected in series, respectively. The housing of each ofthe battery modules MOD1 to MOD18 has a positive-polarity terminal thatcorresponds to the positive electrode of a battery cell positioned atone end on the higher potential side (simply referred to as the “batterycell on the higher potential side” below, e.g., a battery cell C1 of thebattery module MOD1), and a negative-polarity terminal that correspondsto the negative electrode of a battery cell positioned at the other endon the lower potential side (simply referred to as the “battery cell onthe lower potential side” below, e.g., a battery cell C3 of the batterymodule MOD1). Starting from the higher potential side, two adjacentbattery modules among the battery modules MOD1, MOD2, . . . , and MOD18are connected with each other via the respective negative-polarityterminal and the positive-polarity terminal, by one of the conductivemembers CBL1-CBL17. Thus, the battery pack 11 is realized as a body ofserially connected battery modules MOD1-MOD18 (a body of seriallyconnected battery cells C1-C54).

An output voltage required for the vehicle (for example, about 200 V)can be taken out of the battery pack 11 between a positive-polarityterminal V+ extending out of the positive-polarity terminal of thebattery module MOD1 (the positive electrode of the battery cell C1), anda negative-polarity terminal V− extending out of the negative-polarityterminal of the battery module MOD18 (the negative electrode of thebattery cell C54).

A monitor IC 12 is a voltage detection circuit that is implemented as anintegrated circuit (voltage detection IC), and specifically, detectsvoltages of battery cells among the battery cells C1-C54. The monitor IC12 has nine ports connected with respective voltage detection lines asinput lines, and eight channels ch1 to ch8 where each channel has twoadjacent ports among the ports P1 to P9, to detect a voltage. In otherwords, in the monitor IC 12, a port is shared by two adjacent channelsto detect voltages. The channels form multiple (eight in the embodiment)intervals that are connected in series, and used for voltage detectionin circuits (simply referred to as “circuit intervals” below). By apotential difference between endpoints of a circuit interval, it ispossible to detect a voltage of a circuit element (a battery cell or aconductive member) in the circuit interval. In the following, theendpoints of the circuit intervals used for voltage detection may bereferred to as “detection points”.

The monitor IC 12 may include, for example, a multiplexer and an ADconverter(s) that are connected with the ports P1 to P9. With amultiplexer and an AD converter, the monitor IC 12 may be configured toapply time-division multiplexing to voltages of the channels ch1 to ch8(analog signals) by the multiplexer, and to convert the voltages intocorresponding digital signals by the AD converter, to output theconverted digital signals to the battery ECU 20 (or the microcomputer22). Alternatively, the monitor IC 12 may be configured to include eightAD converters to convert voltages of the channels ch1 to ch8 (analogsignals) into corresponding digital signals by the multiplexer,respectively, to output the converted digital signals to the battery ECU20 (or the microcomputer 22). In the following, seven monitor ICs 12included in the battery monitor apparatus 1 will be referred to as the“monitor ICs 12-1 to 12-7”, to distinguish them by respective codes whennecessary.

Note that the number of circuit intervals (or circuit elements such asbattery cells included in the circuit intervals) in which voltages canbe detected by a monitor IC 12, or the number of channels, is set toeight in the embodiment as an example, which may be set discretionally.

Each of the monitor ICs 12-1 to 12-7 has two or more battery cellsallocated that are connected in series, as targets of voltage detectionamong the battery cells C1-C54. The monitor IC 12-1 has the batterycells C1 to C6 allocated, as targets of voltage detection. Also, themonitor ICs 12-2 to 12-7 have six battery cells allocated, respectively,among 48 battery cells C7 to C54, that are connected in series from thehigh potential side, as targets of voltage detection. To put it plainly,the monitor ICs 12-2, 12-3, 12-4, 12-5, 12-6, and 12-7 have the batterycells C7 to C14, C15 to C22, C23 to C30, C31 to C38, C39 to C46, and C47to C54 allocated, respectively, as targets of voltage detection.

As described above, the monitor ICs 12-1 to 12-7 detect the voltages ofthe battery cells by potential differences between the endpoints of thecircuit intervals that include the battery cells as targets of voltagedetection, respectively. Specifically, the monitor ICs 12-1 to 12-7 candetect the voltages of the battery cells as targets of voltagedetection, respectively, by having every two adjacent ports connectedwith two voltage detection lines that are connected with electrodes ofthe battery cells, or wires connected with the electrodes.

As described above, the monitor IC 12-1 detects the voltages of thebattery cells C1 to C6 that correspond to the battery modules MOD1 andMOD2.

To detect the voltages of the battery cells C1 to C3 that are connectedin series in the battery module MOD1, the monitor IC 12-1 uses a shareddetection point that corresponds to electrodes of two adjacent batterycells, when detecting the voltages of the two adjacent battery cells. Inother words, the monitor IC 12-1 uses a port shared by two channels fordetecting voltages of two adjacent circuit intervals (or battery cellsincluded in the circuit intervals). For example, a voltage detectionline that is connected with a detection point corresponding to theelectrodes connecting the battery cells C1 and C2 in the battery moduleMOD1, is connected with the port P3. Then, the monitor IC 12-1 detectsthe voltage of the battery cell C1 by the port P2 and the port P3(constituting the channel ch2) where P2 corresponds to the detectionpoint on the positive electrode side of the battery cell C1, and detectsthe voltage of the battery cell C2 by the port P3 and the port P4(constituting the channel ch3) where P4 corresponds to the detectionpoint on the negative electrode side of the battery cell C2. In thisway, the monitor IC 12-1 detects the voltage of three battery cells C1to C3 in the battery module MOD1 by four ports P2 to P5 (channels ch2 toch4).

Similarly, for detecting the voltages of the battery cells C4 to C6 thatare connected in series in the battery module MOD2, the monitor IC 12-1uses a shared detection point that corresponds to electrodes of twoadjacent battery cells, when detecting the voltages of the two adjacentbattery cells. In other words, the monitor IC 12-1 uses a port shared bytwo channels for detecting voltages of two adjacent circuit intervals(or battery cells included in the circuit intervals). For example, avoltage detection line that is connected with a detection pointcorresponding to the electrodes connecting the battery cells C5 and C6in the battery module MOD1, is connected with the port P8. Then, themonitor IC 12-1 detects the voltage of the battery cell C5 by the portP7 and the port P8 (constituting the channel ch7) where P7 correspondsto the detection point on the positive electrode side of the batterycell C5, and detects the voltage of the battery cell C6 by the port P8and the port P9 (constituting the channel ch8) where P9 corresponds tothe detection point on the negative electrode side of the battery cellC6. In this way, the monitor IC 12-1 detects the voltage of the threebattery cells C4 to C6 in the battery module MOD1 by four ports P6 to P9(channels ch6 to ch8).

Thus, by using shared detection points that correspond to electrodes ofadjacent battery cells, the number of wires inside and outside of themonitor IC 12-1, and the number of ports for voltage detection can bereduced. Therefore, the circuit size of the monitor IC 12-1 can besmaller, and the cost can be less. In the following, use of shareddetection points that correspond to electrodes of adjacent battery cellsin the monitor ICs 12-2 to 12-7, aims at the same effects.

Also, in addition to the voltages of the battery cells C1 to C6, themonitor IC 12-1 detects the voltage of the conductive member CBL1 thatconnects the negative-polarity terminal of the battery module MOD1 withthe positive-polarity terminal of the battery module MOD2, whichcorresponds to a voltage drop in the conductive member CBL1.Specifically, two detection points are separately disposed on theconductive member CBL1 (for example, on both ends): one detection pointis on the negative electrode side of the battery cell C3 on the lowerpotential side of the battery module MOD1; and the other detection pointis on the positive electrode side of the battery cell C4 on the higherpotential side of the battery module MOD2. Thus, the monitor IC 12-1 candetect the voltage of the conductive member CBL1 that connects thebattery modules MOD1 and MOD2 with each other, by the channel ch5constituted with the port P5 that corresponds to the detection point onthe negative electrode side of the battery cell C3, and the port P6 thatcorresponds to the detection point on the positive electrode side of thebattery cell C4.

That is to say, the monitor IC 12-1 detects the voltages of the batterycells C3 and C4 adjacent to the conductive member CBL1, and also detectsthe voltage of the conductive member CBL1 that connects the batterycells C3 and C4 with each other.

In this way, by detecting potential differences between the endpoints ofseven circuit intervals that are connected in series, the monitor IC12-1 detects the voltages of seven circuit elements included in thecircuit intervals (the battery cells C1, C2, and C3, the conductivemember CBL1, and the battery cells C4, C5, and C6). Note that themonitor IC 12-1 detects the voltages of the battery cells C3 and C4adjacent to the conductive member CBL1 by the potential differencebetween the endpoints of the circuit interval that does not include theconductive member CBL1.

Also note that the port P1 (or the channel ch1) of the monitor IC 12-1is not used.

In the same way, each of the monitor ICs 12-2 to 12-7 detects thevoltages of eight battery cells that are connected in series andallocated among the battery cells C7 to C54 from the higher potentialside. The monitor ICs 12-2 to 12-7 detect the voltages of adjacentbattery cells by using shared detection points on connection sides ofadjacent battery cells which are targets of voltage detection. Forexample, a voltage detection line that is connected with a detectionpoint corresponding to the electrodes on the connection sides of thebattery cells C7 and C8, is connected with the port P2 of the monitor IC12-2. Then, the monitor IC 12-2 detects the voltage of the battery cellC7 by the port P1 and the port P2 (constituting the channel ch1) whereP1 corresponds to the detection points on the positive electrode side ofthe battery cell C7, and detects the voltage of the battery cell C8 bythe port P2 and the port P3 (constituting the channel ch2) where P3corresponds to the detection point on the negative electrode side of thebattery cell C8. That is to say, each of the monitor ICs 12-2 to 12-7detects the voltages of eight battery cells that are targets of voltagedetection by nine ports P1 to P9 (channels ch1 to ch8).

More specifically, the monitor ICs 12-2 to 12-7 detect the voltages ofeight battery cells over two or more battery modules. A detection pointon the negative electrode side of a battery cell on the lower potentialside of a battery module is disposed at one end on the lower potentialside of a conductive member (the side closer to a lower battery module)that is connected with the negative-polarity terminal of the batterymodule. That is to say, the monitor ICs 12-2 to 12-7 detect the voltagesof the battery cells on the lower potential sides of the battery modulesMOD3 to MOD17 by potential differences between the endpoints (betweenthe detection points) of circuit intervals including the conductivemembers CBL3 to CBL17. For example, the detection point on the negativeelectrode side of the battery cell C9 on the lower potential side of thebattery module MOD3 is disposed at one end on the positive-polarityterminal side of the battery module MOD4 of the conductive member CBL3that is connected with the negative-polarity terminal of the batterymodule MOD3. Then, the monitor IC 12-2 detects the voltage of thebattery cell C9 by a potential difference between the endpoints (betweenthe detection points) of the circuit interval corresponding to theconductive member CBL3, by using the ports P3 and P4 (constituting thechannel ch3). That is to say, when detecting the voltages of two or morebattery cells over adjacent battery modules, the monitor ICs 12-2 to12-7 detect the voltage of a battery cell on the lower potential side ofa battery module such that the detected voltage includes a voltage dropof a conductive member that connects the battery module with itsadjacent lower battery module.

Note that although omitted in FIG. 3, between the ports of the batterycells C1-C54 (detection points on the positive-pole side and detectionpoints on the negative-pole side), and the ports of the monitor ICs 12-1to 12-7, additional elements may be disposed, such as filter circuits toremove noise, cell balancing circuits (equalizer circuits) to solvedeviation of charged states (voltages) of the battery cells C1-C54, andfuses.

The battery ECU 20 is an electronic control unit to monitor a state ofthe battery unit 10 (battery cells C1-C54). The battery ECU 20 includesan isolator 21 and the microcomputer 22, and is connected with theHV-ECU 30 to enable communication between the devices via an in-vehicleLAN or the like.

Note that the battery ECU 20 (or the microcomputer 22) is connected withthe monitor ICs 12-1 to 12-7 by a daisy-chain.

The isolator 21 is a known insulation interface that electricallyinsulates the battery unit 10 as a high-voltage system from themicrocomputer 22 as a low-voltage system, through which the monitor IC12 (12-7) in the battery unit 10 and the microcomputer 22 cancommunicate with each other.

The microcomputer 22 is a processor to execute various calculationprocesses, by running various programs stored in a ROM (Read OnlyMemory), on a CPU (Central Processing Unit).

The microcomputer 22 transmits a command to the monitor IC 12 (12-7), tohave the monitor ICs 12-1 to 12-7 periodically detect voltages of thebattery cells C1-C54 and the voltage of the conductive member CBL1, andto transmit detection signals corresponding to the detected voltages. Asdescribed above, the microcomputer 22 and the monitor ICs 12-1 to 12-7are connected in the daisy chain. Therefore, the command transmittedfrom the microcomputer 22 is transferred through the monitor IC 12-7,the monitor IC 12-6, . . . , and the monitor IC 12-1, in this order.Then, in response to the command, the detection signals corresponding tothe voltages of the battery cells C1-C54 detected by the monitor ICs12-1 to 12-7, are transferred through the monitor IC 12-1, the monitorIC 12-2, . . . , and the monitor IC 12-7, in this order, and then,transmitted from the monitor IC 12-7 to the microcomputer 22. In thefollowing, the communication periodically executed between themicrocomputer 22 and the monitor ICs 12-1 to 12-7 may be referred to asthe “periodic communication”.

Also, the microcomputer 22 calculates the voltages of the battery cellsC1-C54 and the voltage of the conductive member CBL1, based on thedetection signals transmitted from the monitor ICs 12 (12-1 to 12-7). Inthe following, the voltages calculated by the microcomputer 22 based onthe detection signals transmitted from the monitor ICs 12 (12-1 to12-7), will be referred to as the “voltages detected by the monitor ICs12 (12-1 to 12-7)”.

Also, based on the voltages of the battery cells C1-C54 and the voltageof the conductive member CBL1 detected by the monitor ICs 12 (12-1 to12-7), the microcomputer 22 monitors states (voltages, currents, statesof charge (SOC), states of health (SOH) and the like) of the batterycells C1-C54. For example, the microcomputer 22 may monitor the SOCs bymonitoring whether the voltages of the battery cells C1-C54 are within aprescribed range (between a prescribed upper limit and a prescribedlower limit). Then, if one of the battery cells C1-C54 has its voltagereach the upper limit or the lower limit, the microcomputer 22 maydetermine that it is overcharged or over-discharged, to control chargingand discharging the battery cells C1-C54 via the HV-ECU 30 thereafter.Specifically, the microcomputer 22 transmits a signal indicating thatone of the battery cells C1-C54 is overcharged (an overcharge signal),or a signal indicating that it is over-discharged (an over-dischargesignal) to the HV-ECU 30. Also, the microcomputer 22 may determine thatan overcurrent is flowing if the current flows in the battery cells C1to C54 (or the battery pack 11) exceeds a prescribed threshold, tocontrol charging and discharging the battery cells C1-C54 via the HV-ECU30 thereafter. Specifically, the microcomputer 22 transmits a signalindicating that the overcurrent is flowing in the battery cells C1 toC54, to the HV-ECU 30. State monitoring of the battery cells C1 to C54by the microcomputer 22 will be described later in detail.

Note that the microcomputer 22 may transmit information relating statesof the battery cells C1-C54 other than the above signals (overchargesignal, over-discharge signal, and overcurrent signal), for example, asignal indicating a current state of charge (charge rate), and a signalindicating a current SOH.

The HV-ECU 30 is an electronic control unit to execute various controlrelating to the vehicle, including charge and discharge control of thebattery unit 10 (battery cells C1-C54). The HV-ECU 30 may be constitutedwith, for example, a microcomputer, and may execute various controlprocesses including charge and discharge control, by running variousprograms stored in a ROM, on a CPU.

The HV-ECU 30 may execute the charge and discharge control based oninformation transmitted from the battery ECU 20 (the microcomputer 22).For example, if receiving an overcharge signal from the microcomputer22, the HV-ECU 30 may execute controlling so that charging is checked(inhibited) and discharging is accelerated on the battery cells C1-C54.Also, if receiving an over-discharge signal from the microcomputer 22,the HV-ECU 30 may execute controlling so that charging is acceleratedand discharging is checked (inhibited) on the battery cells C1-C54.Also, if receiving an overcurrent signal from the microcomputer 22, theHV-ECU 30 may execute controlling so that charging and discharging areinhibited on the battery cells C1-C54.

The HV-ECU 30 is configured to be capable of controlling operations ofthe engine 40, the motor 50, and the generator 60. That is to say,depending on a traveling state of the vehicle and/or an operation by thedriver, the HV-ECU 30 controls the engine 40, the motor 50, and thegenerator 60, to execute the charge and discharge control of the batteryunit 10 (battery cells C1-C54).

Note that the HV-ECU 30 controls operations of the motor 50 and thegenerator 60 by controlling driving the motor inverter 70 and thegenerator inverter 80. Also, the HV-ECU 30 may execute controlling theengine 40, the motor 50 (or the motor inverter 70), and the generator 60(or the generator inverter 80) via other ECUs that directly control theengine 40, the motor 50 (or the motor inverter 70), and the generator 60(or the generator inverter 80).

Next, state monitoring of the battery cells C1 to C54 by the batterymonitor apparatus 1 (or the battery ECU 20) will be describedspecifically.

As described above, when detecting the voltages of two or more batterycells over adjacent battery modules, the monitor ICs 12-2 to 12-7 detectthe voltage of a battery cell on the lower potential side of a batterymodule such that the detected voltage includes a voltage drop of aconductive member that connects the battery module with its adjacentlower battery module. Therefore, imbalance may be generated between thevoltage of a battery cell on the lower potential side of a batterymodule, and the voltages of battery cells other than the battery cell,which are detected by the monitor ICs 12-2 to 12-7. This will bedescribed specifically using FIG. 4 below.

FIG. 4 is a diagram that compares the voltage of a battery cellpositioned at the end on the lower potential side of a battery module,with the voltage of the other one of the battery cells, which aredetected by the monitor ICs 12-2 to 12-7. Specifically, the figureillustrates the voltages of the battery cells C8 and C9 in the batterymodule MOD3 detected by the monitor IC 12-2.

Here, Vs8 and Vs9 in the figure represent the voltages of the batterycells C8 and C9 detected by the monitor IC 12-2, respectively. Also, E8and E9 represent electromotive forces of the battery cells C8 and C9,respectively. Also, Ro8 and Ro9 represent internal resistances of thebattery cells C8 and C9, respectively. Also, I represents a currentflowing in the battery cells C8 and C9 (or the battery pack 11) wherethe current is flowing in the positive direction when the battery cellsC8 and C9 are being charged, and in the negative direction when thebattery cells C8 and C9 are being discharged. Also, R represents theresistance of the conductive member CBL3.

Adjacent battery cells in the battery modules MOD3 to MOD18 may bedirectly connected with each other by their electrodes (the positiveelectrode and the negative electrode), or may be connected by aconnection member between the electrodes very close to each other.Therefore, even with use of shared detection points that correspond toelectrodes of adjacent battery cells as described above, the monitor ICs12-2 to 12-7 can detect the voltages of battery cells, other thanbattery cells on the lower potential sides of the battery modules MOD3to MOD18, with comparatively good precision. That is to say, the voltageVs8 of the battery cell C8 detected by the monitor IC 12-2 can berepresented by Vs8=E8+Ro8·I.

On the other hand, adjacent battery modules are connected via one of theconductive members CBL1 to CBL17. In general, the conductive membersCBL1 to CBL17 have a certain length due to layout restriction in thevehicle and maintainability, and the resistance is greater than that ofconnection members for adjacent battery cells in the battery modulesMOD1 to MOD18. Note that as described above, when detecting the voltagesof two or more battery cells over adjacent battery modules, the monitorICs 12-2 to 12-7 detect the voltage of a battery cell on the lowerpotential side of a battery module such that the detected voltageincludes a voltage drop of a conductive member that connects the batterymodule with its adjacent lower battery module. Therefore, the voltage ofthe battery cell on the lower potential side of each of the batterymodules MOD3 to MOD17 detected by the monitor ICs 12-2 to 12-7 isdetected as a value that includes a voltage drop in the correspondingone of the conductive members CBL3 to CBL17. This implies that thevoltage Vs9 of the battery cell C9 detected by the monitor IC 12-2 isrepresented by Vs9=E9+Ro9·I+R·I.

Even if actual voltages of the battery cells C8 and C9 are virtually thesame (E8≈E9, Ro8≈Ro9) as single elements, imbalance is generated betweenthe voltages of the battery cells C8 and C9 when detected by the monitorIC 12-2, due to the amount of the voltage drop (R·I) in the conductivemember CBL3.

In this way, since the detected voltage of the battery cell C9 includesthe voltage drop in the conductive member CBL3, a detected value ishigher than the actual voltage of the battery cell C9 when charging, orlower than the actual voltage of the battery cell C9 when discharging.In such a case, if the configuration described above is adopted thatchecks (inhibits) charging the battery cells C1 to C54 when the voltageof one of the battery cells C1 to C54 reaches the prescribed upper limitvalue, charging may be checked (inhibited) even when the actual voltagedoes not reach the upper limit value. Also, if the configurationdescribed above is adopted that checks (inhibits) discharging thebattery cells C1 to C54 when the voltage of one of the battery cells C1to C54 reaches the prescribed lower limit value, discharging may bechecked (inhibited) even when the actual voltage does not reach thelower limit value. This causes inconvenience that the voltage range (orthe charged state) is narrowed to permit charging or discharging thebattery cells C1 to C54. Especially, for a hybrid vehicle as in theembodiment, if the voltage range (or the charged state) is narrowed topermit charging or discharging, the operational frequency andoperational load of the engine 40 are increased, and consequently, thefuel efficiency may get worse.

Thereupon, in addition to the voltages of the battery cells C1 to C54detected by the monitor ICs 12 (12-1 to 12-7), the battery monitorapparatus 1 according to the embodiment detects the voltage of theconductive member CBL1 by the monitor IC 12-1, to monitor states of thebattery cells C1 to C54. Specifically, based on the voltage of theconductive member CBL1, the battery monitor apparatus 1 calculatesvoltage drops by the conductive members included in the voltages of thebattery cells detected by potential differences between the endpoints ofthe circuit intervals including the conductive members, among thevoltages of the battery cells C7 to C54 detected by the monitor ICs 12-2to 12-7. Then, the battery monitor apparatus 1 monitors states of thebattery cells C1 to C54 considering the voltage drops.

As an example of a method of considering the voltage drops, there is amethod that corrects the voltage of a battery cell detected by thepotential difference between the endpoints of a circuit interval thatincludes a conductive member, among the voltages of the battery cells C7to C54 detected by the monitor ICs 12-2 to 12-7. Also, as anotherexample, there is a method that changes the monitor condition (theprescribed upper limit value and lower limit value to determineovercharging and over-discharging of the battery cells C1 to C54described above) of battery cells whose voltages are detected bypotential differences between the endpoints of circuit intervals thatinclude respective conductive members, by voltage drops. In thefollowing, a case will be described that adopts the former method thatcorrects the voltage of a battery cell detected by the potentialdifference between the endpoints of a circuit interval that includes aconductive member (the voltages of battery cells on the lower potentialsides of the battery modules MOD3 to MOD17).

FIG. 5 is a flowchart that schematically illustrates an example of avoltage correction process executed by the battery monitor apparatus 1(or the battery ECU) 20 according to the embodiment (a process tocorrect the voltage of a battery cell positioned at one end on the lowerpotential side of each of the battery modules MOD3 to MOD17, detected bythe monitor ICs 12-2 to 12-7). Note that a process based on theflowchart is started when the ignition of the vehicle is turned on(IG-ON), or the microcomputer 22 of the battery ECU 20 is reset.

At Step S101, the microcomputer 22 executes a process to learn addressesof the monitor ICs 12-1 to 12-7 in the daisy-chain connection.Specifically, the microcomputer 22 transmits an address learning commandto the monitor ICs 12-1 to 12-7. In response to receiving the addresslearning command, the monitor ICs 12-1 to 12-7 transmit signals thatcorrespond to their own addresses to the microcomputer 22, respectively.Then, by receiving the signals, the microcomputer 22 learns theaddresses of the monitor ICs 12-1 to 12-7.

At Step S102, the microcomputer 22 executes a periodic communication.Specifically, as described above, the microcomputer 22 transmits acommand that requests transmission of detection signals that correspondto the voltages of the battery cells C1 to C54, and the voltage of theconductive member CBL1, and then, receives the detection signalstransmitted from the monitor ICs 12-1 to 12-7 in response to thecommand.

At Step S103, the microcomputer 22 reads the voltage of the conductivemember CBL1 (corresponding to the voltage drop in the conductive memberCBL1) calculated based on the detection signal received at Step S102,from the internal memory or the like.

At Step S104, based on the voltage of the conductive member CBL1 read atStep S103, the microcomputer 22 calculates a current value (I in FIG. 4)that flows in the battery cells C1 to C54 (or the battery pack 11). Forexample, the microcomputer 22 may store a resistance value of theconductive member CBL1 that has been obtained in advance by anexperiment, a simulation, or trimming work at factory shipment of thevehicle and the like, in the internal memory. Then, the microcomputer 22may calculate the current value by dividing the voltage of theconductive member CBL1 detected by the monitor IC 12, by the storedresistance of the conductive member CBL1.

Note that the microcomputer 22 may calculate the current valueconsidering other factors such as temperature. For example, themicrocomputer 22 may determine (calculate) the resistance valueconsidering temperature detected by a temperature sensor (notillustrated) or the like, based on a convert formula or a map(representing change of the resistance value by temperature) stored inadvance in the internal memory, to calculate the current value from theresistance value.

At Step S105, the microcomputer 22 reads the voltage of a battery cellto be corrected among the voltages of the battery cells C1 to C54,calculated based on the detection signals received at Step S102. That isto say, the microcomputer 22 reads the voltages of battery cellsdetected by the potential differences between the endpoints of circuitintervals that include the conductive members (the voltages of batterycells on the lower potential sides of the battery modules MOD3 toMOD17).

At Step S106, using the current value calculated at Step S104, themicrocomputer 22, corrects the voltages of the battery cells to becorrected that are detected by the monitor ICs 12-2 to 12-7. Forexample, the microcomputer 22 may store resistance values of theconductive members CBL3 to CBL17 that have been obtained in advance byan experiment, a simulation, or trimming work at factory shipment of thevehicle and the like, in the internal memory. Then, the microcomputer 22may correct each of the voltages of the battery cells to be corrected bysubtracting the product of the stored resistance value and thecalculated current value, as the voltage drop of the corresponding oneof the conductive members CBL3 to CBL17.

Note that if the resistance values of the conductive members CBL3 toCBL17 are virtually the same, the microcomputer 22 may correct thevoltages of the battery cells to be corrected by subtracting, thevoltage of the conductive member CBL1 read at Step S103 (correspondingto the voltage drop in the conductive member CBL1) directly from thevoltages of the battery cells to be corrected. In this case, Step S104may be omitted.

At Step S107, the microcomputer 22 determines whether to terminate theperiodic communication, due to an ignition off (IG-OFF) of the vehicleor the like. If having determined not to terminate the periodiccommunication, the microcomputer 22 goes back to Step S102, and repeatsSteps S102 to S107; or if having determined to terminate the periodiccommunication, the microcomputer 22 terminates the current process.

Note that if the resistance values of the conductive members CBL3 toCBL17 are virtually the same, the voltage correction process by thebattery ECU 20 (or the microcomputer 22) may be executed in analogcircuits in the monitor ICs 12-2 to 12-7. That is to say, aconfiguration is adopted in which a detection signal that corresponds tothe voltage of the conductive member CBL1 detected by the monitor IC12-1 can be transferred to the monitor ICs 12-2 to 12-7. Then, based onthe detection signal that corresponds to the voltage of the conductivemember CBL1, the analog circuits in the monitor ICs 12-2 to 12-7 mayexecute respective processes to cancel the voltage drops by theconductive members CBL3 to CBL17.

In this way, by using the monitor IC 12-1 among the monitor ICs 12-1 to12-7, the battery monitor apparatus 1 according to the embodimentdetects the voltage of the conductive member CBL1 that corresponds tothe voltage drop in the conductive member CBL1 in addition to thevoltages of the battery cells C1 to C6. Then, the battery monitorapparatus 1 monitors the states of the battery cells C1 to C54, based onthe voltages of the battery cells C1 to C54 detected by the monitor ICs12-1 to 12-7, and the voltage of the conductive member CBL1 thatcorresponds to the voltage drop in the conductive member CBL1.Specifically, based on the voltage of the conductive member CBL1, thebattery monitor apparatus 1 monitors the states of the battery cells C1to C54 by calculating the voltage drops of the conductive membersincluded in the voltages of the battery cells detected by the potentialdifferences between endpoints (between detection points) of circuitintervals that include the conductive members, and considering thevoltage drops. Thus, as described above, even when the voltages of thebattery cells C1 to C54 are detected with use of shared detection pointsthat correspond to electrodes of adjacent battery cells, effects of thevoltage drops in the conductive members connecting the battery modules(imbalanced voltages) can be excluded. Therefore, states of the batterycells included in the battery pack can be monitored appropriately, andthe inconvenience described above, such as worsened fuel efficiency dueto the effects of the voltage drop, can be avoided.

Also, in the embodiment, the effects of the voltage drops in theconductive members that connect the battery modules with each other, canbe excluded, by having at least one channel among the channels forvoltage detection of the monitor ICs 12-1 to 12-7 used for voltagedetection of the conductive member. Therefore, to exclude the effects ofthe voltage drops in the conductive members that connect the batterymodules with each other, it is not necessary to avoid a monitor IC thatdetects voltages of battery cells over multiple battery modules. Also,it is not necessary to change the number of channels of a monitor ICappropriately, to match a configuration of a battery pack, and not todetect voltages of battery cells over multiple battery modules.Therefore, it is possible to monitor battery cells appropriately withoutincreasing the cost and the circuit size.

Also, since the current flowing in the battery pack 11 (or the batterycells C1 to C54) can be calculated by detecting the voltage of theconductive member CBL1 by the monitor IC 12-1, it is not necessary toprovide a current sensor or the like to monitor the state of the currentflowing in the battery pack 11. That is to say, the battery monitorapparatus 1 according to the embodiment can monitor the state of thecurrent flowing in the battery cells C1 to C54 (and whether it is anovercurrent) based on the current flowing in the battery cells C1 to C54calculated by using the voltage of the conductive member CBL1 detectedby the monitor IC 12-1.

Note that in the embodiment, the voltage of a battery cell on the lowerpotential side of a higher potential battery module among adjacentbattery modules is detected by the potential difference between theendpoints of a circuit interval that includes a conductive memberconnecting the adjacent battery modules with each other, but theconfiguration is not limited to that. That is to say, the voltage of abattery cell on the higher potential side of a lower battery moduleamong adjacent battery modules may be detected by the potentialdifference between the endpoints of a circuit interval that includes aconductive member connecting the adjacent battery modules with eachother. For example, the monitor IC 12-2 may detect the voltage of thehigher potential battery cell C10 of battery module MOD4, instead of thevoltage of the battery cell C9 on the lower potential side of thebattery module MOD3, by the potential difference between the endpointsof the circuit interval that includes the conductive member CBL3.

Also, in the embodiment, the voltage of the conductive member CBL1 isdetected by the monitor IC 12-1. Instead, one of the voltages of theconductive members CBL2 to 17 may be detected by the corresponding oneof the monitor ICs 12-1 to 12-7. For example, the monitor IC 12-1 maydetect the voltages of the battery cells C4 to C6 by the channels ch5 toch7, and may detect the voltage of the conductive member CBL2 by thechannel ch8. In this case, the monitor IC 12-1 detects at least one ofthe voltages of the battery cells C3 and C4 by the potential differenceof the circuit interval that includes the conductive member CBL1, and atleast one of the detected voltages of the battery cells C3 and C4 iscorrected based on the detected voltage of the conductive member CBL2.

Also, in the embodiment, although the monitor IC 12 (12-1) that detectsthe voltage of the conductive member CBL1, detects both voltages of thebattery cells C3 and C4 adjacent to the conductive member, the monitorIC 12 (12-1) may detect at least one of the voltages of the batterycells adjacent to the conductive member. For example, to detect thevoltage of the conductive member CBL2, the monitor IC 12-1 may detectthe voltage of the battery cell C6 at the channel ch7 by the potentialdifference between the endpoints of a circuit interval that does notinclude the conductive member CBL2, and may detect the voltage of theconductive member CBL2 at the channel ch8.

Modified Example

Next, a modified example of the above embodiment will be described.

In the embodiment described above, the voltage of one conductive memberis detected. In the modified example, voltages of two or more conductivemembers are detected, and based on the voltages of two or moreconductive members, the voltages of the battery cells detected by thepotential differences between the endpoints of circuit intervals thatinclude the conductive members are corrected. Thus, effects of agingdegradation of conductive members can be avoided.

Specifically, a conductive member may have its resistance changed byaging degradation. Also, imbalance of loads among the conductive membersthat is caused depending on a decreased battery capacitance due todifferences of use histories among battery cells may generate differentdegradation development among the conductive members, and may introducevariations among the resistance values of the conductive members. Forexample, the resistance value of the conductive member CBL1 may changedue to the aging degradation, or even if the resistance value of theconductive member CBL1 has hardly changed, degradation development ofthe other conductive members (any of the conductive part members CBL2 toCBL17) may come earlier to change their resistance values.

Thereupon, by detecting the voltages of two or more conductive members,effects of the aging degradation of the conductive members can beavoided. For example, by taking an average (including the load average)of current values of a battery pack calculated from detected voltages oftwo or more conductive members, respectively, effects of change of theresistance of some conductive members by degradation can be checked, tomaintain the precision of the calculated current value comparativelyhigher. Also, if the resistance values of conductive members withoutdegradation are virtually the same, a degree of degradation developmentof the conductive members can be determined by detecting and comparingthe voltages of two or more conductive members, and the voltage of aconductive member having comparatively less degradation may be adoptedto correct the voltages of the battery cells to be corrected.

In this way, in the modified example, by detecting the voltages of twoor more conductive members, it is possible to avoid effects of the agingdegradation of the conductive members, and effects of differences ofdegradation development among the conductive members, to continue statemonitoring of the battery cells appropriately.

The embodiments have been described in detail. Note that embodiments arenot limited to the above specific embodiments, but various changes,substitutions, and alterations could be made.

Also, the battery monitor apparatus according to the embodimentsdescribed above may be used for monitoring states of unit batteriesincluded in a battery pack that is built in an electric vehicle otherthan a series-parallel-type hybrid vehicle (a range extender vehicle, anelectric vehicle having only a motor as a driving force source, or thelike).

Also, the battery monitor apparatus according to the embodimentsdescribed above may be used for monitoring a state of a battery packthat is built in an apparatus other than a vehicle (for example, abattery pack for a stationary electric storage device).

The invention claimed is:
 1. A battery monitor apparatus, comprising: aplurality of unit batteries connected in series; a battery packincluding a plurality of battery modules connected in series byconductive members, each of the battery modules including two or more ofthe unit batteries connected in series among the plurality of the unitbatteries; a plurality of voltage detection ICs configured to detectvoltages of circuit elements including the plurality of unit batteriesand the conductive members in a plurality of circuit intervals connectedin series, by potential differences between endpoints of the circuitintervals, and to detect voltages of two or more of the unit batteriesconnected in series among the plurality of the unit batteries; and anelectronic control unit configured to monitor states of the unitbatteries; wherein a first one of the voltage detection ICs detects avoltage of at least one of the two unit batteries coupled to a first oneof the conductive members, and detects the voltage drop of the firstconductive member coupled to the two unit batteries, wherein theelectronic control unit monitors the states, based on the voltages ofthe unit batteries detected by the voltage detection ICs, and thevoltage drop of the first conductive member detected by the first one ofthe voltage detection ICs, wherein when detecting the voltages of twounit batteries coupled to one of the conductive members other than thefirst conductive member whose voltage is detected by the first one ofthe voltage detection ICs, each of the voltage detection ICs detects thevoltage of at least one of the two unit batteries by the potentialdifference between the endpoints of the circuit interval including theone of the conductive members, wherein the electronic control unit isfurther configured to correct the voltages of the unit batteriesdetected by the potential differences between the endpoints of thecircuit intervals including the conductive members among the voltages ofthe unit batteries detected by the voltage detection ICs, based on thevoltage drop of the first conductive member detected by the first one ofthe voltage detection ICs, wherein the electronic control unit monitorsthe states, based on the corrected voltages.
 2. The battery monitorapparatus as claimed in claim 1, wherein the electronic control unitmonitors the states, based on a current flowing in the battery packcalculated from the voltages of the conductive members detected by thefirst one of the voltage detection ICs.